Oil circuit breaker



Aug. 18, 1936. s, BARFOED 2,051,196

' OIL CIRCUIT BREAKER Original Filed Sept. 10, 1950 4 Sheets-Sheet 1 oneI 7 I 38 E 37 INVEN TOR.

A TTORNEYS.

1936- s. BARFOED OIL CIRCUIT BREAKER 4 Sheets-Sheet 2 Original FiledSept. 10, 1930 INVENTOR.

BY 1&4 vmd- CQWd/ZO ATTORNEYS.

Aug. 18, 1936. s. BARFOED OIL CIRCUIT BREAKER 4 Sheets-Shet 3 OriginalFiled Sept. 10, 1950 IN V EN TOR.

m2 ATTORNEYS.

S. BARFOED OIL CIRCUIT BREAKER Original Filed Sept. 10, 1930 4Sheets-Sheet 4 fi F .5.

INVENTOR.

ATTORNEYS.

Patented Aug. 18, 1936 UNITED STATES PATENT OFFICE Substituteforapplication Serial No. 480,874, September 10, 1930. This applicationAugust 13, 1984', Serial No. 739,583

10 Claims.

This invention relates to oil circuit breakers particularly intended foruse in alternating current circuits, the present application being asubstitute for my former application Serial Number 480,874, entitled Oilcircuit breaker, filed September 10, 1930-.

There are several forms of oil circuit breakers now in use and generallythe arrangement consists of a pair of stationary contacts and a pair'ofmovable contacts mounted to separate or close in a vertical directionthrough the oil.

When opening such a circuit breaker, an arc is drawn between each pairof stationary and movable contacts and an. arcs position will, at thebeginning of the stroke, be nearly stationary in the path of the movingcontact; the oil vaporizes and gasifies'to form a large bubble whichwill be inefficiently cooled since the surrounding oil must flow towards'itfrom rest by convection; Upon further movement'of'the contacts, theelectrodynamic force: of the current flowing in the arc comes more intoplay to move or bend out the arc to enlarge its loop. This'bending ofthe arc will tend to cool it chiefly in: its middle region.

Both contacts andthe ends of the" arc will still beinefliciently'sco-ured and cooled by the: oil; the

upper contact, because-it 'is stationary, and the lower or movingcontact, because of cavitation pockets formedin the oil by its movementthrough the oil; therefore, the arc'will maintain itself a comparativelylong time from the: continuedion production from the hot cc'ntactsvandfrom the hot gas bubble attheends of the arciwhere its position isnearly stationary with respect to'the arc. The path taken by" thecontacts in passing through the oil; the amount of cavitation pro- Theheat wave generated by the-pulsating power in each successive half cyclewill produce, in: like manner, pulsating quantities of: gases "andvapors from the contact materials and decomposition products of the oil;

5 The object of the present invention is to generally improve andsimplify the construction and operation of circuit breakers of this"character; to

provide a circuit breaker in which the contacts" canbe separated atahigh rate ofspeedi; to pro-' vide contacts which present a minimum areato the path of travel through the oil so as to reduce resistance ofmovement to a minimumand to substantially eliminate cavitation and undueagitation of the oil; to provide a pair of contacts which 5 arepivotally mounted and movable in unison on arcs away from each othersoas to pull or move the arc downwardly and horizontallythrough the oilduring" the breaking operation; to. provide contacts which are dividedinto Widely spaced 10 pairs of main contacts and each pair having anintermediate auxiliary contact to carry the arc during the breakingoperation; to provide a barrier to confine the arc between the auxiliarycontacts during the breaking operation; to form 15 pockets in thebarrier to contain oil in such quantities as to become instantaneouslyvaporized by the heat of the are as it sweeps overthe same and therebycause a series of explosions tending to disperse or blow out the arc;and, further, to provide means for deflecting and directing oil over thefaces of the auxiliary contacts and between the same to reduce burningand to break up and further quench the arc.

The circuit breaker is shown by way of illustration in the accompanyingdrawings, inwhich- Fig. 1 is a side elevation ofthe oil circuit breaker,said view'being partially in section and showing the switch or contactoperatingmechamsm;

Fig.2 is an enlarged central vertical section of the n circuit breakerjv Fig. 3 is an enlarged central 'sectionof the barrier member, said viewalso showing different positions assumed by the contacts duringseparation thereof; I

Fig. 4 isia crosssection taken on line IVIV of Fig. 3;" I V Fig. 5 is aview similar to Fig. 3, showing the connecting links whereby'the'contact arms are actuatedyand Fig. (iis an end view of Fig. 5.

Referring to the drawings in detail and particularly Figs; 1 and 2,Aindicatesa tank or similar containerprovided witha bottom section 2 anda cover section 3. Supported by the cover section and extendingtherethrough are a pairof insulatingbushings such as indicated at 4 and5 and extending through the bushings are conductor bars BandBd on thelower ends of which are '50- pivotally mounted, as at 1' and 8, contactor switch arms 9 and H]. The lower ends of the armsyse'e, Figs. 3, 4 and6, are fork-shaped toform a pair of main contacts ll; These contacts arewidely separated so that theym ay straddle" a barrier ,line positionshown in Fig. 2.

member generally indicated at l2. The central and lower end of each armis provided with a deflector plate l3. The sides of the deflector platesare carried downwardly, as shown at M, and they form bearings for a pairof auxiliary contacts generally indicated at 15 and I6. These contactsare pivoted between the bearing lugs l4 and are free to move about thepivots to a limited degree, the amount of pivotal movement beingdetermined by stop lugs Mia. The auxiliary contacts are urged to aposition where the stop lugs lea stop their movement by springs such asindicated at ll. The function of the deflecting plates l3 and theyielding action of the auxiliary contacts will hereinafter be described.

The barrier member indicated at 12 may be constructed of any suitableinsulating material and it is supported with relation to the bottomsection 2 by means of a pedestal insulator such as shown at 68. Thebarrier member in side elevation is substantially wedge-shaped. A grooveI9 is formed in each side of the upper face of the barrier member andthese grooves are connected by a center slot 26, the adjacent faces ofwhich are grooved as shown at 2! to form successive superposedcylindrical pockets for the reception of oil, as will hereinafter bedescribed. The main function of the barrier block is to confine the areformed between the auxiliary contacts during separation thereof orbreaking of the circuit and it also functions to disperse or blow outthe arc, as will hereinafter be described. In addition thereto, itcarries a pair of contact members 22 which are engaged by the maincontact arms H when a circuit is closed.

In the operation of a switch or circuit breaker of this character, it isessential that the separating action of the contacts shall be as rapidas possible. Means must accordingly be provided whereby rapid separationor opening of the contacts may be accomplished. The operating mechanismemployed in the present instance is best illustrated in Figs. 1 and 2.It consists of a pair of links 25 pivotally connected at their lowerends to the respective contact arms 9 and Ill, as shown at 26, andpivotally connected at their upper ends, as shown at 21, to a plungerbar 28. The upper end of the plunger bar, see Fig. 1, is connected witha lever 29 pivoted as at 30. The opposite end of this lever is connectedwith a connecting rod 3! which, in turn, is pivotally connected to acrosshead 732 and a piston 34 which operates a cylinder such as shown at35. This cylinder is provided with a pair of three-way valves such asshown at 36, which are connected with a suitable source of fluid supplythrough means of a pipe 31 and which is also provided with a dischargepipe 38. The source of fluidsupply is maintained at a predeterminedpressure so that the speed of the piston 34 and the contact arms 9 andI0 may be determined, this being of considerable importance, as willhereinafter appear. The valves 36 are connected by common link mechanism39 and this is in turn actuated by an operating lever M), as shown.

In actual practice it will be understood that the container A issubstantially filled with oil so as to maintain the switch mechanism andthe barrier member in a submerged condition. If a circuit through thebreaker has been closed, the contact arms and contacts will assume theposition shown in Fig. 2 and when the circuit is broken the contact armswill assume the dotted To break the circuit it is only necessary for theoperator to swing the operating lever 40 from the full line positionshown in Fig. 1 to the dotted line position indicated at 40c. Thisreverses the position of the valves 36 and as such admits the fluidunder pressure to the lower side of the piston 34 and at the same timepermits the fluid previously delivered to the cylinder to dischargethrough the upper valve 36 and the discharge pipe 38 and, as the fluidemployed is maintained at a predetermined pressure, the speed of thepiston and the mechanism actuated thereby can be determined. Theoperating mechanism of course performs only one function, to wit, thatof separating or closing the contacts.

Since the circuit breaker here illustrated is particularly intended foralternating current circuits, it is to be remembered that the power of asingle phase supply is pulsating due to the sinusoidal variation incurrent and voltage with respect to time; and for explanation unity ofpower factor will be assumed. In the present instance, the time requiredto swing the contacts from closed position to full open or separatedposition is known and for the purpose of de scription it will be assumedthat while the contacts sweep over the barrier member I2, six halfcycles or impulses take place. Five of these pockets are illustrated,see Figs. 3 and 4. The are produced during separation of the contactsis, in the present instance, confined between the auxiliary contacts I 5and I6 by means of the barrier block l2, and as these contacts alignwith the slots 19 and the slot 20 having the enlarged pockets 2| formedtherein, the arc must pass therethrough. During movement of the contactsand as the half cycle pulsations occur, maximum current flow takes placeat a frequency that causes arcing through the several pockets 2!successively. The body of oil confined in these pockets is comparativelysmall and the current flow and heat produced by the are are so greatthat the oil contained in the respective pockets is vaporized with suchrapidity as to expand with explosive action, hence tending to disperseor blow out the arc. The oil pockets 2| become longer and longer as thecontacts sweep downwardly over the barrier and as each body of oilexplodes it tends to disperse or blow out the ionized decompositionproducts as the current decreases to zero, making it more and moredifiicult for the current to reestablish the are as the current flowagain reaches maximum during each half cycle of flow.

The dispersing or blowing out action of the arc just described is notthe only action depended upon to quench the arc. For instance, byreferring to Fig. 3, it will be noted that the deflecting plates [3 areprovided. These will, during the downward and outward sweep of thecontact arms, function as nozzles and discharge oil under high velocitydownwardly over the faces of the auxiliary contacts and between the samein the direction of the arrows indicated at a. The high velocity of theoil is obtained by the rapid motion of the contact arms in an outwarddirection and the oil thus delivered over the faces of the auxiliarycontacts and between the same is depended upon to reduce any burningaction and the formation of vapors which would tend to sustain the arc.In the present structure the current contacting leads passing throughthe insulators 4 and 5 and the arms 9 and I0 form a loop in whichcurrent flows. Such a loop is subject to an electrodynamic force tendingto enlarge it on 75..

the well: known". principle. of: electromagnetism.-. When the contactarms separatmandzthea arc:isx struck, the. same. el'ectrodynamic; force!isalso active onv the arc: duegto the. current.flowing throughit;and.the.:arc:iszthereby enlarged; curved:

and;pro.pelled in a downward-direction, asrindie catedbythedotted-lineb..- This is another-reason;

for directing. the oilijetsin the directionlofi arrows a, see Eig:3;.asthe oil so: directed. is pro.- jected'with high velocity againsttheaarc formed: between the. contact. membersand in the same directionas the electrodynamic force relative to the are, .thus tending to.furtherenlarge: and expand-.the arc-to.causedisruptionthereof.

Also.=it. should-be notedthat the contactarm sweep. downwardly. and"outwardly about the pivots l and 8-.Thisisalso.importantias-zit"rapidly. increasesthespacing between thecontacts,

thereby lengtheningethe arc, and asthma contactsv atthesametimemove'downwardly, there is a tendency to. pullithearc into a body offresh cool oil, this .action being exceedingly-important as it.

rapidly. cools the are core and, furthermore, interposes a larger andlarger: body of oil; thexresistance.ofiwhichsoonbecomes too great forthe arc to penetrate.

Another important feature to be considered is the forking of the maincontact arms at their lower ends to form a pair of main contacts I I oneach arm. These contacts are widely separated and are disposed onopposite sides of the barrier member I2. These contacts, when inengagement with the stationary contact blocks 22, carry the main currentflow when a circuit is established. They are held in engagement with thecontact blocks 22 with pressure due to the upward pull on the links 25.When the contact arms are brought together to close the circuit, theauxiliary con tacts first engage and, as they are pivotally andyieldingly supported between the bearing lugs M by means of the springsI'I, they will give until the main contacts ll engage the contact blocks22. During separation of the contacts when breaking the circuit, themain contacts II will leave the contacts 22 and will move a considerabledistance before the auxiliary contacts [5 and i6 are disengaged, as theywill be held in engagement with relation to each other by the springs I!until the stop lugs l6 prevent further movement. At that point theyseparate and as they have been carrying the current flow during thepreliminary separation of the main contacts, the arc is establishedbetween the auxiliary contacts, hence preventing arc formation betweenthe main contacts. Burning action, if any, will accordingly take placebetween the auxiliary contacts, leaving the main contacts unaffected.Another important feature to be considered is the fact that the maincontacts present a comparatively small area when passing through theoil, as they are substantially knife-like in formation, hence cuttingthrough the oil during the rapid movement of the contact arms withoutproducing any material agitation or cavitation in the oil. This isobviously desirable as it is cavitation more than anything else thattends to continue arcing.

While certain features of the present invention are more or lessspecifically described, I wish it understood that various changes may beresorted to within the scope of the appended claims. Similarly, that thematerials and finishes of the several parts employed may be such as themanufacturer may decide, or varying conditions or uses may demand.

' Having: described: my inventiom. what. I claim and desire: to)securerbya Letters Patent is-" 1-. In; a; circuitzbreakeri of? thecharacter described, a. container: for: oil, azpair ofi pivotally'mounted arms submerged: in the oil, apair of spaced; maini contacts oneach: 'arm, an auxiliary contact on. each arm and disposed between themain contacts, means for imparting movement to the arms about their:pivots toseparate: the contacts; means whereby. the auxiliary contactsare. maintained: in engagement until a substantial separation betweenvthe main. contacts: has takenplace; and apain ofbarrier:plates":disposed" in. the container in-Ja position. where the 1main contacts willmove parallellto the said plates while the auxiliarycontacts will move along the'edgesof the plates and the are formedduring the separatiomofithe auxiliary contacts will be confined betweenthe: plates and the auxiliary contacts 2..In a-= circuit breaker: ofthecharacten described, a: container for oil, a pair: of pivotally'mounted arms submerged inthe: oil, a pair of spaced main contacts oneacharm, an auxiliary contact on each arm and disposed between the"mainv contacts, means forimparting movement to the arms about theirpivots to separate the contacts, means whereby the auxiliary contactsare maintained in engagement until a substantial separation between themain contacts has taken place, a pair of barrier plates disposed in thecontainer in a position where the main contacts will move parallel tothe said plates while the auxiliary contacts will move along the edgesof the plates and the are formed during the separation of the auxiliarycontacts will be confined between the plates and the auxiliary contacts,and means for directing oil under high velocity between the faces of theauxiliary contacts and downwardly between the barrier plates.

3. In a circuit breaker of the character described, a pair of movablecontacts, a barrier member cooperating therewith, said member comprisinga pair of plates constructed of insulating material spaced to form aslot for the reception of oil and the adjacent faces of the plateshaving spaced grooves formed therein forming successively disposedenlarged bodies of oil, and means for moving the contacts at oppositeends of the slot and exteriorly thereof sothat the are only will passthrough the slot.

4. In a circuit breaker of the character described, a pair of contactmembers, means for moving the contact members from a closed to an openposition, and a barrier interposed between the paths of movement of saidcontact members, said barrier being constructed of insulating materialand having elongated pockets extending through it in a position to alignone at a time with said contact members as they traverse their path ofmovement, said pockets progressing in length toward the full openposition of the contact members.

5. In a circuit breaker of the character described, a pair of contactmembers, means for moving the contact members from a closed to an openposition, and a barrier interposed between the paths of movement of saidcontact members, said barrier being constructed of insulating materialand having elongated pockets extending through it in a position to alignone at a time with said contact members as they traverse their path ofmovement, said pockets decreasing in cross sectional area toward thefull open position of the contact members.

6. In a circuit breaker, a pair of plates constructed of insulatingmaterial and spaced to form a slot, a pair of contact members, andmovable exterior of said plates from a closed to an open position in theplane of said slot and at opposite ends of said slot whereby the arcformed between said contact members will pass through the slot. g

7. In a circuit breaker, a pair of plates constructed of insulatingmaterial and spaced to form a slot, 2. pair of contact members, movableexterior of said plates from a closed to an open position in the planeof said slot and at opposite ends of said slot whereby the are formedbetween said contact members will pass through the slot, and means fordirecting a flow of oil through the arc.

'8. In a circuit breaker, a pair of plates constructed of insulatingmaterial and spaced to form a slot, a pair of contact members, means tomove said contact members from a closed to an open position in the planeof said slot and at opposite ends of said slot whereby the are formedbetween said contact members will pass through the slot,,and meansactuated by movement of the contact members for directing a flow of oiltransversely through the are.

9. In a circuit breaker of the character described, a container for oil,a pair of arms each having a contact member at one end, said arms beingpivoted at their other ends so that when a circuit is broken the contactends of the arms will swing away from each other in the plane of theelectrodynamic force produced in the loop of the arc which is formedduring the breaking of the circuit, and means for directing a flow ofoil into the arc and transversely thereof between the contacts in thesame direction as the electrodynamic force to control and quench thearc.

10. In a circuit breaker, a pair of plates constructed of insulatingmaterial and spaced to form a slot, a pair of contact members movableexterior of said plates from a closed to an open position in the planeof said slot and at opposite ends of said slot whereby the are formedbetween the contact members will pass through the slot, and means formaintaining the movable contact members and the spaced plates submergedin a liquid arc quenching medium.

SVEND BARFOED.

